Aging, chronic diseases, and acute events such as a stroke and hip fracture result in a reduction in physiological reserve and functional decline The fundamental tenet of the Applied Clinical Physiology Core (RC-3) is that physical deconditioning and "learned" non-use propagate functional declines in older people. This provides a biological rationale to implement exercise training to improve multiple physiological systems in older persons hindered by disability. The mission of RC-3 is to provide a core for the standardized cardiovascular, functional, and metabolic evaluations of OAIC research subjects and assist investigators in determining the mechanisms by which exercise rehabilitation strategies enhance function and recovery in older adults with disabling diseases such as stroke or hip fracture. This Core focuses on the following aims: 1. To perform medical assessments and cardiovascular screening of research volunteers entering OAIC studies in order to ensure patient safety and eligibility. 2. To standardize the conduct of exercise physiology, body composition, and metabolism measures that will define the phenotype of disability by characterizing the pathophysiology and functional performance of older, disabled volunteers in OAIC research. 3. To assess whether the exercise rehabilitation interventions increase cardiovascular fitness and ambulatory physical activity levels, improve body composition and metabolic profiles. 4. To train junior faculty investigators in geriatrics and gerontology in the performance of applied exercise physiology research relevant to exercise -based rehabilitation, in disability and aging. 5. To provide an educational and consultative resource for all investigators interested in exercise rehabilitation in aging, and the assessment of exercise rehabilitation, cardiovascular physiology and ambulatory function in the OAIC. These specific aims represent an enrichment of the contributions that the core has made in the previous OAIC as well as a new CDP designed to determine the effects of exercise rehabilitation on functional performance in older adults infected with HIV, and new pilot and exploratory (P/E) projects and Junior Faculty Award (JFA) projects in stroke, robotics, and hip fracture. Thus, the RC-3 plays a critical role in integrating and linking the RCs, the CDPs, JFA projects, P/E projects in the study of exercise design, and its conduct, and the measurement of cardiovascular fitness, metabolism and body composition. Lay: The mission of the Applied Physiology Core (RC-3) is to assess the effects of exercise rehabilitation on exercise performance, ability to perform tasks of daily living, muscle and fat mass, and risk factors for heart disease in older subjects disabled by chronic stroke, hip fracture, and other disabling diseases.